Aliminum

[Instar]

Yes, and did you know that washing your reflectors of the salt crystals back into the tank adds even more Al?
Al, a heavy metal, is very toxic to all marine life. Its the kalk reactor that adds Al because it stirs up the precipitated sediment. That can be avoided however. The precipitate or sediment after mixing kalk is NOT supposed to end up in the tank. If you use a premix of kalk, let it settle out, and then put only the clear supernate into the tank or the reactor, only the real solution will be in there and not the Al as well as all the other contaminates a Kalk reactor dumps into the tank. Most people just dump the kalk into the reactors and let it mix around, dumping all the precipitates into the tank. That preciptiate carries a number of heavy metal contaminates. In regard to the Al in brine shrimp, that study was of one brand a very long time ago. I'm not so sure there is as much Al contaminate in the brine we have today. Honestly, the amount of PO4 and PO4 bound vitamins used to fortify the brine is of at least some concern if AL is. And the amount of NH3 in shelved planktonic products people have liked to dump on their corals at night feedings over the years has NH3 through the roof. The benefit of dumping all this stuff into your tank is obvious -- you have to do more water changes.

[Tim Marvin]

Water changes....I'm all for that...

[captexas]

If it is a heavy metal, won't it settle into the rock and sand bed and therefore not get removed during routine water changes?

[GaryP]

pH.

[GaryP]

What Larry means by heavy metal is that its atomic weight is heavy. Its present as an ion, not as a particle and therefore would be soluble.

Aluminum, and other metals in Kalk will precipitate as Aluminum Hydroxide. Most metals are not very soluble at high pH.

[captexas]

So . . . does it stay floating around in the water table then or will it settle out?

[GaryP]

Its like Calcium, it will stay dissolved until something takes it out.

Aluminum is technically not a heavy metal and its toxicity is a lot lower than what we normally consider toxics metals like heavy metals such as cadmium, lead, mercury, and chromium. However, everything has a toxic level, even water.

Yes there are sources of aluminum that we add to our aquariums, including the salt we use. On the same note there are inputs of other metals as well. I believe if you are doing regular water changes these iinputs can be offset.

Here's a quote from the article that was mentioned above.


In a recent survey of 23 reef aquaria, Shimek claimed that aluminum levels ranged from 0.070 to 0.32 ppm, with a mean of 0.173 ppm .23 That same study claimed that Instant Ocean Contained 0.110 ppm aluminum.

That tells me that aluminum may not be as large an issue as some people may be led to believe.

[captexas]

Ok, just curious as I've read stuff in the past about some elements/compounds being absorbed by the live rock or settling into the sand bed and you are not able to get rid of it.

[GaryP]

Generally, if something is precipitated its not going to be as available for biological uptake.

You are probably th8inking about things like copper. Precipitated copper may leach out slowly, but its toxicity is so much higher than aluminum its more of an issue.

One of the supposed advantages of using Kalk is that it precipitates phosphate as calcium phosphate.

[GaryP]

I just got through reading the article and the one thing it doesn't account for are any export mechanisms. By that I mean precipitation, filtration, skimming, or water changes. The article only looked at mechanism of import.

import - export = concentration

[dan]

WOW!!!!!!! that was heavy man. :shades

[Instar]

Well basically you are all right. Some of the heavy metals, IE: copper, aluminum, lead, chromium, tin stay available as ionic forms. However, at normal pH in sea water (our tanks), with available carbonates, these will tend to be incorporated into precipitates, assimulated into tissue and made insoluable, unavailable complexes. They are layered in and under the coraline algaes on the rocks, taken up in macro algaes, adsorbed deep into the sand bed and turned into skeletal structure where they are no longer an issue and can not be removed from the tank simply by water changes. Carbonated skelital structure matrixes are extremely stable. Until, they get deep into the substrate and are then again made available due to the low pH and anaerobic bacterial decomposition. And, even in there, the greater majority of such precipitates is supposed to be very stable and permanent. If the pH was to go to 2.0 deep in the sand bed, that would be quite another story, but, it won't go that low. Therefore most metal precipiates are quite stable and insoluable. If a tank is maintained by regular water changes, any of these ions that do come into play if ever they do, are removed. There is an issue of build up in ionic, chelated and bioavailable forms of metals over the first couple years but, this can be at least partially overcome by doing a couple of water changes of a greater percentage and/or more frequently than the monthly 10% during the year. The biggest issue would be the return of copper as that one is the more easily dissolved precipitate at the lower pH of the deep sand bed. However copper is not as readily available as the others might be. In other words, if you are using RO/DI without additives and no meds in the tank, there shouldn't be any source for copper (no brass ball valves or housings/impellors). And then if there was, it can only exist for any length of time at about 8ppm at a pH of 8.0 and up. I believe that the various elevated levels of metals as Josh and Gary referrs to in Shimek's publication, accounts directly for the difference in larval survival rates between the different mixes.